2 parts water
1 part fine fabric cleanser
Combine two parts water and one part fine fabric cleanser. Dip makeup brushes into the solution. Rinse in clean water. Submerge brushes again into a baking soda and water mixture to soften the bristles. Rinse again in clean water. Blot excess and allow to dry.
You can also wash them with shampoo and conditioner once a month. Squeeze out excess water, lay them flat overnight and reshape them when dry.